There is continuing interest in miniaturizing wireless communication devices, including their antenna systems. Therefore, such antennas and constituent antenna elements are typically closely packed. The small distance between the antennas has the potential to affect not only their radiation pattern, but also the mutual coupling between them, hence increasing the risk of interference and performance degradation.
Prior art solutions do not provide satisfactory decoupling or are difficult to implement. For example, electromagnetic bandgap structures typically require a relatively large area, which goes against the miniaturization of the antenna systems. Decoupling networks are also too large, are not wideband enough, or do not improve isolation sufficiently. Some prior approaches use resonant parasitic elements to try to decouple two closely spaced antennas by creating an extra coupling field through the parasitic elements that attempts to cancel out the direct coupling field between the two antennas and suppress the mutual coupling between them, but this approach is inherently narrow band and frequency sensitive (i.e., a design for operation at one resonant frequency is generally not applicable to operation at different non-resonant frequencies), requires a relatively complex and expensive design process, and, at best, typically results in relatively poor antenna-antenna isolation.
Thus, there is a need in the art for a compact and inexpensive-to-implement yet relatively effective wideband antenna isolation system.